Heart and vascular disease are major problems in the United States and throughout the world. Conditions such as atherosclerosis result in blood vessels becoming blocked or narrowed. This blockage can result in lack of oxygenation of the heart, which has significant consequences since the heart muscle must be well oxygenated in order to maintain its blood pumping action. In addition, blockages in cranial areas or in vessels adjacent the brain could lead to considerable complications such as stroke.
Occluded, stenotic, or narrowed blood vessels may be treated with a number of relatively non-invasive medical procedures including percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA), and atherectomy. Angioplasty techniques typically involve the use of a balloon catheter. The balloon catheter is advanced over a guidewire such that the balloon is positioned adjacent a stenotic lesion. The balloon is then inflated and the restriction of the vessel is opened. During an atherectomy procedure, the stenotic lesion may be mechanically cut away from the blood vessel wall using an atherectomy catheter.
During angioplasty and atherectomy procedures, embolic debris can be separated from the wall of the blood vessel. If this debris enters the circulatory system, it could block other vascular regions including the neural and pulmonary vasculature. During angioplasty procedures, stenotic debris may also break loose due to manipulation of the blood vessel. Because of this debris, a number of devices, termed embolic protection devices, have been developed to filter out this debris.
Typically, embolic protection filtering devices include a filter attached to a shaft or filter wire. Because the vasculature of a patient may be very tortuous, it may be desirable to combine a number of performance features into the filter wire. For example, it is sometimes desirable that the filter wire have a relatively high level of pushability and torqueability, particularly near its proximal end. It is also sometimes desirable that the filter wire be relatively flexible, particularly near its distal end. A number of different filter wire structures and assemblies are known, each having certain advantages and disadvantages. However, there is an ongoing need to provide alternative filter wire structures and assemblies.